Power take-off ring gears are typically mounted on the radially outer surface of a clutch housing in the transmission of a vehicular drive train. In such an arrangement an annular clutch drum is presented as the radially outermost element of a rotatable clutch housing. The radially outer surface of the clutch drum is splined to effect a rotational driving connection with a power take-off ring gear received thereon. Two annular grooves are machined in the radially outer surface of the clutch drum, and a snap ring, or other retaining device, is received within each groove to embrace the hub of a ring gear therebetween and thereby maintain the ring gear at the desired axial location along the clutch drum.
In such prior art arrangements the clutch drum is also extended for a sufficient axial extent to permit machining one or more additional annular grooves on the radially inwardly directed surface of the annular clutch drum to receive, and/or position, several components of the transmission which are conveniently located interiorly of the clutch drum.
The known prior art arrangements thus required that the clutch drum have a rather significant axial extent. In view of the fact that clutch housings are generally metallic castings, the axial extent required for the clutch drum as well as the several machining steps required to be performed upon both the radially outer, and the radially inner, surfaces of the clutch drum contribute significantly to the overall manufacturing cost of the clutch housing. The manufacturing cost includes not only of the direct cost of the materials and the labor required to machine the several grooves but also the cost incurred by scrapping unsatisfactory clutch housings, the likelihood of which is increased not only because of the complexity of casting a clutch housing having an axially extended clutch drum but also because of the machining steps required to provide the several grooves utilized in the prior art arrangement.
In addition, the axial extent of the clutch drum required by the prior art arrangement increases the mass of the clutch drum and thereby effects a concomitant increase to the moment of inertia as well as the radius of gyration for the clutch housing. That is, the clutch drum is located at the radially outermost extent of the clutch housing so that any excessive mass thereof tends to increase the moment of inertia and the radius of gyration for the overall clutch housing.